Asked in Premeth MDCAT 2025 LR-04 — Electromagnetism, Transition Elements 2025Moderate

A solenoid 15 cm long has 300 turns of wire. A current of 5 A flows through it. What is the magnitude of the magnetic field inside the solenoid?

Correct answer: C. 4π x 10-3

  • A. 75 x 10^7 T
  • B. 60 x 10+3 T
  • C. 4π x 10-3
  • D. 750π x 10+3

Explanation

The magnetic field inside a solenoid is given by the formula:B=μ0nIwhere:B = Magnetic field (T)μ0 = Permeability of free space (4π×10−7n = Number of turns per unit length (N/L)I = Current (A)Given data:N=300N = 300N=300 turnsL=15L = 15L=15 cm = 0.15 mI=5I = 5I=5 AFirst, calculate n:n=NL=3000.15=2000 turns/mNow, calculate BBB:B=(4π×10−7)×(2000)×(5)Approximating π≈3.1416B≈4×3.1416×10−3

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